True grit: (noun) firmness of mind, unyielding courage, fortitude.

15-year-old Luis has true grit.

On this particular morning, he’s engaged in what appears to be a kind of freestyle footrace with his therapist—and it’s hard to tell just who is motivating whom.

“Come on, man. … You can do this!”

Nick Hamilton, P.T.A., is in lockstep with his patient as they move like lightning across the spacious rehabilitation floor.

Luis lives for this stuff. Barely 15 but looking more like 18, his physical size and level of discipline suggest he might have been a pro athlete if things had worked out differently. But they didn’t. A lack of oxygen at birth left him with cerebral palsy—and a daily struggle to get his body to fall in line with what his brain has in mind.

Just now, Luis is at full-tilt, his upper body stooped, fighting to conquer the physical contortions so common with cerebral palsy, and looking for all the world like he’s about to topple forward onto the floor mats. But Luis knows what he’s doing. He’s in complete control, and he’s moving ahead.

It wasn’t like this 18 months ago. Before Luis started therapy at Johns Hopkins All Children’s Child Development and Rehabilitation Center, he was having trouble walking, even standing. Nick and another skilled therapist, Ashley Roscoe, P.T., have helped him break free of some of the patterns that limit his movement, and he has made real progress.

“Luis is one of the hardest working kids I’ve ever seen,” Nick says. “He’s amazing. But he’ll be college-bound in a few years, and I want to do the work now to make sure he has every opportunity.”

Nick’s motivation is to help kids like Luis reach their maximum potential.

But his inspiration – well, that comes from a different place.

A few yards away, just on the other side of the wall, is Nick’s own son, 12-year-old Isaac.

Isaac has cerebral palsy also—specifically, spastic quadriplegic cerebral palsy—understood to be the most severe type. Isaac is a handsome boy—with thick dark hair and bright eyes that are fully willing to engage a new friend. He uses a wheelchair for now, has limited speech, and, like so many children with cerebral palsy, struggles to get command of the primitive reflexes that take over his body and keep him locked into postures that don’t serve him.

“He’s my inspiration for life, honestly. There’s not a single thing I do in my day that does not involve him being at the center of it,” Nick says.

Isaac did indeed change his dad’s life. Nick at one time had big dreams of being a touring musician, and was on that track—until he realized there was something bigger that he could do—that he must do. He went back to school to become a physical therapist assistant and began making a real difference for his son, and for so many other kids with physical challenges.

Inspired by the therapists and the resources at this rehabilitation center, Nick applied and was hired—and he can’t imagine bringing Isaac anywhere else for care.

Isaac is scheduled for intensive therapy with Rachelle Lee, O.T., on this day. Lately he has been arching his back and keeping his body inclined to the right. The therapist uses a pulley system to calm the spasms and bring things back to center. She’ll work on helping Isaac get in touch with muscles he doesn’t have ready access to, and then strengthening those muscles—so he can take some power back over his body.

“Hey, buddy. How’s it going?”

Isaac’s dad has stopped by between his patients’ sessions to check in on his boy. He pulls a bright yellow plastic banana up to his ear, as if answering a phone call.

“Oh, hello, … it’s grandma.” Straight-faced. “She wants to talk to you.”

Isaac breaks into an impossibly wide grin and releases a peal of laughter. His dad is ridiculous. He cracks him up every time with this one.

For brain-injured children, the level of abilities and the progress they can make covers a spectrum. For some, it may be learning to walk. For others, simply learning to keep their head up so they can use a communication device can be life-changing.

These are children who often get overlooked or underestimated because their progress can seem slow. These are the ones who have Nick’s full attention—and his whole heart.

“I want these kids to be seen. Don’t make assumptions about their cognition or intellect simply because they can’t express themselves exactly like we do. It limits what they can achieve.”

Nick wants for his patients the same things he wants for his own son—to break free from the constraints of other people’s expectations—and to have all of the opportunities life can offer him.

“Isaac is like a bird in cage,” Nick says. “It’s my job to help unlock that cage, so he can fly.”